sends command to redis and returns the reply. It determines the cluster node to
send command to from the first key in @args, sending commands that does not
include key as an argument is not supported. If @args contains several keys,
all of them should belong to the same slot, otherwise redis-server will return
an error if some of the keys are stored on a different node.

Module also defines wrapper methods with names matching corresponding redis
commands, so you can use

attach node with the specified $address to the cluster. If $master_id is
specified, the new node is configured as a replica of the master with the
specified ID, otherwise it will be a master node itself. Address should be
specified as a hash containing host and port elements.

migrates specified slot to the given $destination_node from the current node
responsible for this slot. Destinations node should be specified as a hash
containing host and port elements. For details check Cluster live
reconfiguration section in the Redis Cluster
Specification <http://redis.io/topics/cluster-spec>.

removes node from the cluster. If the node is a slave, it simply shuts the node
down and sends CLUSTER FORGET command to all other cluster nodes. If the node
is a master node, the method first migrates all slots from it to other nodes.